1. Field of the Invention
The present invention relates generally to an exercise and testing apparatus of human motion activity. More particularly it relates to a resistance creating means applied to a person muscular system during an exercise, with a precision and uniformity that provide rehabilitation, diagnostic, therapeutic and/or fitness process exactly as predetermined for the best result in different modes of operation, such as isometric, isotonic, and isokinetic.
2. Description of the Related Art
Conventional equipment that has been developed for a person to improve his/her muscular system more efficiently has also been used for rehabilitation and therapeutic applications. This is caused by relatively low cost of exercise machines versus special equipment.
However, conventional exercise machines do not meet requirements for medical applications. The main reason for the nonconformance is in the mode of load and inertia. The mechanical and electromechanical resistance means of the machines do not provide exact amount of a predetermined load and its application mode. The resistance force created by a flywheel or weights has inertia.
It is exact predetermined load with no inertia that the most important part of diagnostic and rehabilitation processes. For example, to elaborate an effective rehabilitation program after a heart attack, electrophisiological method can be effectively used only with exact amount of muscular work in isometric and isotonic mode. In neurology, any deviation of human motion activity from normal pattern can reveal some pathology. But to research the pattern of an individual motion, the exact predetermined amount of load and mode of its application is needed.
U.S. Pat. No. 5,643,157 to Seliber discloses a device wherein the resistance to motion of an exercise link is a function of the speed of a variable speed rotary driving means. The speed of the rotary driving means is controlled by the user selected value before exercise begins. The resistance to motion stays constant during exercise if the user does not change the resistance. It is well known that the magnitude of muscle force depends on the user""s joint angle. Therefore, muscle force will change according to alteration of the joint angles that, are applied in physical therapy. But, very often, contemporary rehabilitation requires that muscle force be either constant or alter for a predetermined force curve during the joint movement cycle. The seliber""s device does not meet these requirements. Also, the resistance to motion of an exercise link is a function of the direction of the link; the fluid coupling acts as a clutch when the xe2x80x9cheavy negativexe2x80x9d training is used or as a brake during xe2x80x9cpowerxe2x80x9d exercise. Thus, the resistance to motion in this device is time/speed dependent and the sources of the resistance to motion are different for different directions of the joint movement that limits muscle exercise. And finally, the Seliber""s device requires electrical power that limits its portable application. In older U.S. Pat. No. 3,103,357 to Berne the exercise resistance is created by a friction clutch that is operated by hydraulic cylinder and piston means. The fluid pressure of the hydraulic cylinder is measured as frictional resistance. It is well known that friction force may vary depending on surface conditions, grease, humidity, temperature, vibration, difference between coefficients of static and dynamic friction, and cannot be considered a constant magnitude. Although the fluid pressure can be mounted and measured with high accuracy, the exercise resistance will change depending on the frictional force. In U.S. Pat. No. 3,784,194 to Perrine the resistance force is created by input members on opposite ends of the actuatorxe2x80x94either a rotary hydraulic actuator or a conventional cylinder. The stroke of input members is restricted to either the angle of rotation or the length of the actuator. Thus, some modes of exercises that need a long stroke of a piston are impossible, for example, bicycle type exercise.
Even special systems for rehabilitation purpose, occupational therapy, and orthopedic evaluation focus on patient feedback data with given isokinetic speed and isokinetic torque too much more extent than on load mode. Simple and inexpensive equipment to provide the predetermined load is needed.
Simple resistance means to provide non-inertial, non-restrictive in length of motion, and relatively constant load during an exercise are known (see, for example, U.S. Pat. No. 5,529,552). In the known means the resistance force is created by a hydraulic cylinder with manually adjustable flow section area. A piston of the cylinder is connected by a connecting rod with a driven member engaged with a driving member having a cable; whereby a user exercises by pulling the cable against the resistive force generated by said cylinder.
The known resistance devises, as mentioned above, can provide relatively constant load to a muscular system during an exercise, but some limits of accuracy still having place. Those limits are caused by variable deviation of a connecting rod longitudinal axis from stroke direction of the piston during an exercise. The longer the connecting rod the smaller is the deviation and, consequently, the higher accuracy. But one can not elongate the connecting rod infinitely. So, some inaccuracy still remains and impairs results of medical applications.
One object of the present invention is to develop a simple and inexpensive correction means for load stabilization that can be used in combination with known resistance means.
Another object of the present invention is to develop means for predetermined load pattern to meet requirements of medical research both in load applied to a person muscular system and a feedback data acquisition process.
Another object of the present invention is to develop a high accuracy resistance device for an exercise machine that can be used for rehabilitation, therapeutic, and diagnostic purposes.
Another object of the present invention is to develop a compact and easy serviced resistance device that can provide precise amount of load.
In main embodiment of the present invention the resistance device for an exercise machine comprises a driven member to convey a person""s applied exercise load to a resistance means consisting of a hydraulic cylinder having front and rear ends and two separate channels joining these front and rear ends, a piston, a connecting rod to engage the piston with the driven member and transmit force in either direction between the piston and the driven member, and a correction means to maintain a predetermined exercise load and offset load instability that is caused by an angle variation between the connecting rod longitudinal axis and the piston stroke direction. The hydraulic cylinder and both channels are filled with incompressible fluid. The first channel has a first valve that can be adjusted manually by an adjustment means to set an original magnitude of the exercise load. The second channel has a second valve that is adjusted by the correction means. The correction means comprises a cam is coaxial with and secured to the driven member and permanently engaged with the second valve. The cam is secured to the driven member in interchangeable manner and shaped accordingly to a predetermined pattern of the exercise load.
The main embodiment of the present invention, also, comprises an immovable driving member and a movable driving member. The immovable driving member is permanently engaged with the driven member. The immovable driving member has a shaft that is coaxial with and secured to the driven member. The shaft has two free ends to receive and attach any exercise accessories for rotation mode exercise such as bicycle, ski, stairstep, and so on and/or xe2x80x9cpush-pullxe2x80x9d fashion of an exercise. The movable driving member may be engaged with the driven member by an engaging means. The movable driving member has a drum that is coaxial with and secured thereto. The drum has an outside peripheral groove to receive and store a cable that has a free end. The free end is adapted to receive and attach different exercise accessories for pulling mode exercise. The movable driving member is engaged with the driven member during pulling mode exercise that causes unwinding of the cable from the cable drum. In free condition the movable driving member is disengaged with the driven member.
Thus, any pattern of application and precise amount of the exercise load can be applied to a person""s muscular system just by installing the cam having an appropriate periphery. The cam is a compact part to adjust a valve position in a hydraulic cylinder. It is also a simple and inexpensive flat part that can be easily made with any conventional machine tool using a template. By adapting any conventional exercise machine for the resistance device in accordance with the present invention, one can turn simple and inexpensive fitness equipment into precise medical multi-purpose tool.